1. Field of the Invention
This invention relates to photographic systems, particularly to a camera system which responds to various demands placed thereon. When taking a picture with a camera, it is necessary to consider the total photographic system, i.e., the overall photographic environment. The term "photographic system" here is used to define a combination of five elements. The first of these is what is herein called the "object system", and refers to what is generally called "the subject or object to be photographed". It includes the entire object field appearing on the picture plane. The second element is the projection system. This serves to form the optical image of the object system on a recording location such as an image plane. It includes such things as the camera's optical arrangement and the camera assemblage with its various mechanism.
The third element is the recording system for recording the optical image formed by the projection system in a particular form in accordance with a particular desired purpose. In an ordinary camera, the recording system is in the form of a film. However, light sensing means other than photographic light sensing materials participate in the recording process. Thus, it is possible to think of the recording system as an image system with a recorder at its center.
The fourth element is an adjusting system for producing the desired image. The fifth system is the observation system which provides the information to a human for setting the adjusting system.
2. Description of the Prior Art
When we think of a camera device for taking a picture, the photographic system as total system can not be disregarded. What is called the photographic system here is the combination of the five elements, namely the object system, the projection system, the recording system, the adjusting system and the observation system.
Hereby the important system for an ordinary camera is the projection system. Control of this projection system affects the object system, the recording system, the adjusting system and the observation system, and is greatly influenced by the data or the fed back data from these systems. In consequence when one refers to a camera one often means the projection system. Yet it is essential for a camera to establish an overall photographic arrangement and take into account the interaction between various systems.
When such a camera device is thought of from the view point of the photographic work on the actual spot, the problem of the operability which has one of the most important connection with the photographer who is the subject of the projection system should be pointed out beside the problem of the optical and the mechanical precision, or of the efficiency.
The projection system, namely the camera device can, as has already been explained, be divided into two systems, namely the optical arrangement and the body assemblage. The efficiencies of these two are different in accordance with the type of camera. In an ordinary single reflex camera as one example, the optical arrangement involves the focusing efficiency and the aperture adjusting efficiency while the body assemblage involves the shutter efficiency and the finder efficiency. These functions have an important relation with the operability of the camera's aperture determining operation, speed determining operation, focusing operation framing operation and so on.
Of the above, the operation for determining the aperture value and that for calculating the exposure time are mutually dependent for deciding the total exposure. They have different effects on the exposure conditions so that it is necessary to have them operate properly. Specifically when taking a picture the shutter is operated after the focusing operation, the framing operation and the exposure setting operation. It is conventional to control the aperture value and the shutter speed in order to control the exposure. However, one purpose for controlling the aperture value is to the aperture value can be selected in order to makes the main object stand out by focusing out the background. On the other hand, the shutter speed should be selected to prevent the effect of the vibration of the camera and to stop or emphasize movement. Thus when taking a picture the aperture value and the shutter speed are the variables to be selected independently from each other.
In consequence, it goes without saying that the exposure amount should be considered in connection with the photographic system as a whole. In the camera for the exposure value EV=11, there are 11 combinations of the aperture values with the shutter times. These are as follows: (F1: 1/2000 sec.) (F1.4: 1/000 sec.) (F2: 1/500 sec.) (F2.8: 1/250 sec.) (F4: 1/125 sec.) (F5.6: 1/60 sec.) (F8: 1/30 sec.) (F11: 1/15 sec.) (F16: 1/8 sec.) (F22: 1/4 sec.) and (F32: 1/2 sec.). Theoretically, any one of the above combinations produces the same total exposure. However, as mentioned, the aperture and the shutter control not only the total exposure. The aperture affects the depth of field and the image definition while the shutter time directly affects the ability to catch an object in motion and so on. Although they give the same exposure amount, the combination of F1 at 1/2000 sec. produces a different photographic image than F32 at 1/2 sec. when the above-mentioned conditions are taken into consideration.
In a camera with an automatic exposure control device, namely an AE (automatic exposure) camera, a mechanism automatically controls the aperture, the shutter time or their combination for obtaining the proper or the desired exposure of the object for the sensitivity of the film. This contrasts with a manual camera where it is necessary for the photographer to select a proper exposure value and a proper exposure time suited for the photographic purpose on the basis of the object brightness measured by means of the exposure meter and on the basis of the film sensitivity. With an AE camera, the photographer can do other work while taking a picture. This permits efficient and rapid photography so that such cameras are widely used.
Three AE camera systems are presently used. The first one is the so-called shutter or shutter time, priority system. This obtains the proper exposure by automatically controlling the aperture value of the photographic lens as the operation results of the brightness of the object. The shutter time is optionally decided by the photographer. The film sensitivity and so on are given in advance.
The second one is the so-called aperture, or aperture value, priority system for obtaining a proper exposure by automatically controlling the shutter time on the basis of the brightness of the object. The aperture value is selected by the photographer. The film sensitivity and so on are entered in advance.
The third one is the so-called program system for obtaining the proper exposure. Here, the total exposure is automatically calculated on the basis of the object brightness, the film sensitivity and so on. The camera selects the predetermined combination of the aperture value of the photographic lens and the shutter time for obtaining the above-mentioned exposure amount. Thus, neither the shutter time nor the aperture value is decided by the photographer.
Each of the above-mentioned systems has its own advantages. However, each of them also has its own shortcomings.
In the shutter speed priority system, the shutter time can be optionally selected in advance. This is useful for catching a speedy object, for snapshot photography or for telephotography in which the shorter shutter time can be selected to overcome movement of the object or an unstable camera. The depth of field is subject to the aperture value of the photographic lens automatically operated in the camera device in accordance with the shutter time set in advance. Thus, this cannot be said to be a proper exposure control system for taking a picture of a landscape or of a still life. There, depth of field plays in important part in a picture.
In the second system, namely the aperture value priority system, quite the opposite is true. The depth of field can be selected while the shutter time cannot be selected by the photographer. Thus, an automatically produced slow shutter time may result in a blurred picture. Therefore, this cannot be said to be a proper exposure control system for a quickly moving object or for a manually held camera.
In the third system, namely the program system where only the proper exposure is taken into consideration, the photographic conditions cannot be selected by the photographer. In consequence, the above-mentioned program system is used in a simple middle quality camera.
In an AE camera, the shutter time setting dial is at the position equivalent to the aperture value setting ring. In the APEX system series, the shutter time TV and the aperture value AV are in the following relationship for the exposure amount: EQU EV=TV+AV (1)
so that when the shutter time setting dial is handled, the aperture value is varied in order to obtain a certain exposure amount while the aperture setting ring is handled, the shutter time is varied. In consequence, whether the shutter time setting dial or the aperture setting ring is handled, the result is the same, namely there is no need for dividing the case into two.
An aperture priority AE camera known at present is the aperture value priority AE camera in which the automatically controlled shutter time is not transmitted to the photographer at all. If the automatically controlled shutter time is displayed in the viewfinder and the exposure is controlled while the eye is put on the viewfinder, no matter whether the aperture setting ring or the shutter time setting dial is operated, the exposure is controlled while the displayed shutter time is observed in such a manner that the effect is the same as when the shutter time setting dial is handled and the camera can be considered to be a shutter time priority AE camera in this meaning.
Namely, the aperture value priority system AE camera and the shutter time priority system AE camera are reversible in their position depending upon how one uses it and how one thinks.
To summarize the above, the aperture value of the photographic lens and the shutter time are factors very important for deciding the total exposure. When the automatic exposure control efficiency is accorded to the camera, it is necessary to treat the aperture value and the shutter time equally. This is a problem to be especially considered because the reason for according the automatic exposure efficiency to the camera is not only for simplification of the camera handling but also for increasing snap photographic efficiency as well as for allowing the photographer to concentrate more on the framing at the time of camera handling.
Further, before discussing the total exposure, let us consider two systems, namely the object system and the recording system between which the camera as the projection system is located.
At the time of taking a picture, it is necessary for the object system, namely the object field to have its own brightness, called the object brightness and represented BV in APEX system series. Further, the recording system, for example, the photosensitive film has a sensitivity called the film speed normally represented ASA by SV in the APEX system series.
As is well known in the APEX system series, the object brightness BV and the film speed SV are the factors in deciding the exposure amount EV in accordance with the following relationship: EQU BV+SV=EV (2)
The upper and lower limit of the EV range settable in the camera, namely in the projection system, can be made infinite by making the shutter time infinitely long or by the lens attenuating the light. From the viewpoint of a proper exposure, there must be a limit.
In consequence, at the time of taking a picture of an object field at low brightness, namely the BV value is low. It is sufficient to make the film speed SV larger as is clear from relationship (2). On the other hand, at the time of taking an object field with the high brightness, naturally it is sufficient to make the film speed SV smaller. This is an important role in the recording system of the photographic system. Seen from the camera, the recording system can only participate in the film support, the film exchange or the film feeding and not in the alternation of the sensitivity. The only one that is possible is to prepare a film with ultra high sensitivity and to put film with various permiability selectively into the optical path of the projection system so as to alter the sensitivity of the film in an equivalent way. At the present technical level, there is a limit in raising the sensitivity of the film so that it is not easy to use the above method.
On the other hand, when it is desired to obtain a constant exposure while the film sensitivity SV is permitted to be constant, it is necessary to alter the brightness of the object, which is the well known lighting.
Although various methods for the lighting can be through of, now let us take the speed light or flash unit most generally used in connection with a camera.
The intensity of the light from a flash unit is indicated by the guide number. Generally, the aperture value of the lens is decided from the distance to the object and the guide number. However, quite recently, attempts have been made to obtain the proper exposure automatically even while taking a picture with the speed light device. This involves a system in accordance with which light reflected from the object field is detected and the lighting stopped as soon as the amount of the reflected light reaches a predetermined value. Although such a flash unit is part of the object system, it is necessary that it operate in close connection with the camera, i.e., the projection system, because its light time is very short. A device which never disturbs the operability of the camera nor decreases the freedom of the framing by the photographer is especially desired.
Generally, framing as well as focusing are carried out through the viewfinder while operating the camera. Basically, the so-called viewfinder allows the photographer to conform the image of the object to be projected on the film plane. However, at present the viewfinder also serves for focusing.
In a single reflex camera with a built-in light measuring mechanism, light measurement involves the viewfinder.
As mentioned above, the viewfinder plays an important part in the camera handling and can be said to have an important relation with the operability of the camera, for most of the camera operation including the framing and the focusing operation, as the basic operation is carried out through the viewfinder.
Consequently, the information centralizing viewfinder has become widely adopted in such a manner that the photographer can obtain all of the photographic data through the viewfinder. These data have to be displayed in a limited space so that ease of observation and confirmation of the data is required.
Cameras are now used in dim conditions. Hence, it is necessary that the data be displayed in the viewfinder in a dark place just as in a bright place.
Among the camera operations, the framing operation and the focusing operation have a close connection with the portability of the camera body and the operability of the parts. Namely, when taking a picture, it is necessary that the framing be decided by the viewfinder while the camera body is being held in the hands, while the focusing is carried out by operating the distance ring of the lens and the shutter is released at the desired time after operation, for deciding the exposure and others. Hence, it is necessary to arrange the parts in a rational way so as not to prevent the operability of other parts.
To speak more particularly of the operability, the projection system serves to fix a certain moment in the recording system so that it is essential that an absolute counter-measures against the misoperation or the mishandling should be used.
As mentioned above, the operability of the camera can be largely improved by combining the basic operations, such as the operation for deciding the exposure, the framing operation and the focusing operation with out auxiliary operations.
It is an object of the invention to provide a camera capable of operating as a total photographic system.